A critical component of improving patient safety is reducing medical errors. A paucity of information exists on anatomic pathology diagnostic errors and their effect on patient outcomes. Many previously published studies are limited to single institutions and report variable diagnostic error percentages from less than 1 percent to 43 percent of all patients who undergo a biopsy or excisional procedure, with no correlation between error and outcome. A major goal of this project is to establish a Web-based, pathologist-driven, national, voluntary anatomic pathology error database. These data will be used for continuous quality improvement targeted at error reduction and clinical outcomes improvement. Four specific aims will be addressed. First, archival and on-going errors and their associated outcomes, detected by cytologic-histologic correlation and by secondary review of cases at interdepartmental conferences, will be identified retrospectively at four institutions and entered into the database. Each institution will enter their error data into the Web-based database on site, and the date will be sent electronically to the applicant institution for centralized analysis. Second, quarterly and annual quality performance reports, relating to these errors and outcomes, will be generated by the applicant institution research team and disseminated to each institution. These reports will include aggregate diagnostic error and outcome percentages, institution-specific error and outcome percentages, and aggregate and institution-specific error and outcome percentages stratified by multiple potential risk factors for error, such as specimen type. Quantitative analysis of these data will result in objective multi-institutional performance measures. Specific factors (e.g., specimen type, organ, clinical factors, pathologist and practice characteristics) associated with increased risk for diagnostic error will be identified. Third, root cause analysis will be performed to determine the potential sources of errors, and error reduction programs will be implemented at each institution, based on the results of the root cause analysis. Fourth, the success of these interventions will be determined by monitoring post-interventional error and the effects of error on patient outcomes. This project will provide valuable information regarding diagnostic pathology errors; it will set the groundwork for future studies focused on the examination of other types of diagnostic pathology error and the effect of error reduction programs in pathology practice.